Method for converting biodegradable polymers into humus with a low release amount of co2 and use thereof

Abstract

The present invention relates to biodegradable polymers, particularly to a method for converting biodegradable polymers into humus with a low release amount of CO2 and use thereof. A composite material system is formed from the biodegradable polymers and the materials that can slowly release nutrient nitrogen or nutrients nitrogen and phosphorus, in which the mass ratio of carbon to nitrogen in the composite material system is (1-35):1. The materials of the present invention can promote the biodegradable polymers to be converted into soil humus or compost humus, rather than to be converted into greenhouse gas CO2, which is to be emitted into the atmosphere. Therefore, the method is of great significance for energy conservation and emission reduction, green and efficient utilization of biodegradable polymers and efficient and green utilization of biodegradable polymers wastes.

1 . A method for converting biodegradable polymers into humus with a reduced release amount of CO 2 , characterized in that a composite material system is formed from the biodegradable polymers and the materials that release nutrient nitrogen or nutrients nitrogen and phosphorus in a reduced rate, in which the mass ratio of carbon to nitrogen in the composite material system is (1-35):1. 
     
     
         2 . The method according to  claim 1 , characterized in that, in the composite material system, the biodegradable polymers and the materials that release nutrient nitrogen or nutrients nitrogen and phosphorus in a reduced rate are compounded by physically blending the biodegradable polymers and the materials that slowly release nutrient nitrogen or nutrients nitrogen and phosphorus in a reduced rate or by hydrogen bonds interaction among functional groups of each of components of the composite material system. 
     
     
         3 . The method according to  claim 1 , characterized in that the biodegradable polymers are selected from one or a compound of more than one of natural biodegradable polymers and synthetic biodegradable polymers. 
     
     
         4 . The method according to  claim 3 , characterized in that the natural biodegradable polymers are selected from one or a compound of more than one of starch, cellulose, sodium alginate and chitosan, and the synthetic biodegradable polymers are selected from one or a compound of more than one of polyvinyl alcohol, polylactic acid, polybutylene succinate and poly(butylene adipate-co-terephthalate). 
     
     
         5 . The method according to  claim 2 , characterized in that the materials that can release nutrient nitrogen or nutrients nitrogen and phosphorus in a reduced rate are selected from one or a compound of more than one of slow-release fertilizers, controlled-release fertilizers, polyurea, polyacrylamide, polyaspartic acid, protein, melamine copolymer resin and phosphates polymer. 
     
     
         6 . The method according to  claim 5 , characterized in that the fertilizers comprise urea-formaldehyde or its derivatives thereof. 
     
     
         7 . The method for according to  claim 2 , characterized in that the step of physically blending the biodegradable polymers and the materials that release nutrient nitrogen or nutrients nitrogen and phosphorus in a reduced rate comprises the steps of uniformly mixing the biodegradable polymers with the materials that can release nutrient nitrogen or nutrients nitrogen and phosphorus in a reduced rate, and then extruding the uniformly mixed material system by an extruder and pelleting the same to obtain the composite material system. 
     
     
         8 . The method according to  claim 5 , characterized in that the step of compounding the biodegradable polymers and urea-formaldehyde by hydrogen bonds interaction among functional groups of each of components of the composite material system comprises the steps of:
 (1) preparation of a methylolurea powder: adding calculated amounts of formaldehyde and urea into a reactor respectively to obtain a reaction system, adjusting the pH of the reaction system, and reacting the same at a set temperature followed by pouring the reaction solution into a beaker and sealing it, freezing it in a refrigerator, and then extracting and filtering out the remaining liquid to obtain a sample, and finally drying the sample in a vacuum oven and then pulverizing it to obtain a methylolurea powder; and   (2) uniformly mixing the biodegradable polymers with the methylolurea powder, which is a precursor of urea-formaldehyde, prepared in step (1), then extruding the uniformly mixed material system by an extruder and pelleting the same, and subjecting the added methylolurea powder, which is a reaction precursor of urea-formaldehyde, to melt polycondensation reaction in a barrel of the extruder to obtain the composite material system formed from the biodegradable polymers and urea-formaldehyde by the hydrogen bonds interaction among functional groups of each of components of the composite material system; and   the step of compounding the biodegradable polymers and derivatives of urea-formaldehyde by hydrogen bonds interaction among functional groups of each of components of the composite material system comprises the steps of:   (I) preparation of methylolurea powder: adding calculated amounts of formaldehyde and urea into a reactor respectively to obtain a reaction system, adjusting the pH of the reaction system, and reacting the same at a set temperature followed by pouring the reaction solution into a beaker and sealing it, freezing it in a refrigerator, and then extracting and filtering out the remaining liquid to obtain a sample, and finally drying the sample in a vacuum oven and then pulverizing it to obtain the methylolurea powder; and   (II) uniformly mixing the biodegradable polymers with the methylolurea powder, which is a precursor of urea-formaldehyde, prepared in step (I) and phosphate, then extruding the uniformly mixed material system by an extruder and pelleting the same, and subjecting the added methylolurea powder, which is a reaction precursor of urea-formaldehyde, to melt polycondensation reaction in a barrel of the extruder to obtain the composite material system formed from the biodegradable polymers and derivatives of urea-formaldehyde by the hydrogen bonds interaction among functional groups of each of components of the composite material system.   
     
     
         9 . The method according to  claim 1  for promoting the conversion of biodegradable polymers into soil humus or compost humus. 
     
     
         10 . The method according to  claim 9 , characterized in that the composite material system formed from the biodegradable polymers and the materials that release nutrient nitrogen or nutrients nitrogen and phosphorus in a reduced rate is added into the soil or raw composting materials in a mass ratio of its total amount of carbon thereof to the soil or the compost raw materials quality of 1:(60-10900).